Beyond protein & energy

Clint Peck contributing editor

Fri, 2008-08-01 12:00

Balancing rations to provide adequate crude protein and energy is usually the first step in herd sustainability. But while these nutrients are the building blocks of good nutrition, other nutrients like water, minerals and vitamins are the mortar that holds everything together. Water worries We tend to underestimate the importance of a good water supply. A dry cow needs 6-18 gals./day depending on

Balancing rations to provide adequate crude protein and energy is usually the first step in herd sustainability. But while these nutrients are the building blocks of good nutrition, other nutrients like water, minerals and vitamins are the mortar that holds everything together.

Water worries

We tend to underestimate the importance of a good water supply. A dry cow needs 6-18 gals./day depending on conditions. A nursing cow requires at least 5 gals./day more than a dry cow.

Excessive salinity in water can impact cattle performance. Water salinity is a significant problem in many parts of the country. Salinity is measured by total dissolved solids (TDS) — primarily sodium chloride, but may include carbonates, nitrates, sulfates, calcium, magnesium and potassium.

South Dakota State University research shows water with 4,720 ppm TDS and 2,919 ppm sulfates reduced performance in groups of growing steers. Water with 7,268 ppm TDS and 4,654 ppm sulfates not only reduced growth performance but also negatively impacted the steers' health. In the study, water intake decreased linearly with increased TDS and sulfates.

Questions about water quality can be answered by a routine livestock water analysis. Water testing should include attention to livestock water ponds left depleted after hot, dry weather. Unfortunately, finding ways around water salinity are often tougher to come by.

Minerals matter

While we don't necessarily want our cattle drinking salty water, we want salt in the form of the mineral compound sodium chloride in their basal diet. In fact, macro-minerals such as phosphorus, potassium, sulfur, magnesium, sodium and chloride, and trace minerals such as copper, zinc, iodine, manganese, selenium, cobalt and iron, are considered essential for beef cattle diets.

Ruminants' appetite for sodium is so strong that they will return to the exact location of a salt source when they become deficient. In fact, animals' definite appetite for salt can be used as a delivery mechanism to ensure adequate intake of less palatable nutrients and as a feed limiter.

Cattle require 0.25% salt in the diet on a dry matter (DM) basis. Young cattle will consume about 0.1 lb./day and mature cattle up to 0.3 lb./day of salt.

The interactions between trace minerals, animal production and disease resistance are extremely complex. Many factors can affect an animal's response to trace-mineral supplementation. These include duration and concentration of trace-mineral supplementation, physiological status of an animal (pregnant vs. open), the absence or presence of dietary antagonists, environmental factors and the influence of stress on trace-mineral metabolism.

Breed differences in trace-mineral metabolism have also been documented.

Many nutritionists suggest feeding trace mineral salt to the breeding herd free-choice in the form of a mineral block or as loose trace mineral salt. It's important to note that while macro-minerals have important physiological functions in beef cattle, if not supplied in the correct amounts and ratios, specific metabolic diseases and/or toxicities can be produced.

Local veterinarians or nutritionists usually know of local mineral deficiencies. Minerals are needed for vitamin synthesis, hormone production, enzyme activity, collagen formation, tissue synthesis, oxygen transport, energy production and other physiological processes related to growth, reproduction and health.

Recent research shows supplementing trace minerals can positively influence reproductive efficiency by improving uterine involution and reduces the days to breeding (postpartum interval).

Vitamins are vital

The only vitamins of practical concern in everyday beef cattle nutrition are A, D and E.

Vitamin A is most apt to be deficient in high-grain diets and/or when green forages are absent from the diet. Vitamin A requirements are 1,270 IU/lb. of dry matter for pregnant females and 1,770 IU/lb. for lactating females and bulls. Vitamin A can be injected with the benefit lasting 90-100 days.

Cattle exposed to direct sunlight or fed sun-cured forages will receive adequate vitamin D. Vitamin D is also available in an injectable form.

Vitamin E is interrelated with selenium in white-muscle disease in calves, and has been implicated with selenium in reproductive problems in cows. Placental transfer of vitamin E is low, so calves are born with low E levels. However, vitamin E from a lactating cow that received adequate E provides the newborn beef calf with its needs.